The present invention relates to materials used for building products, construction projects, structural objects, mechanical devices and other materials applications. Specifically, the invention concerns composite materials made with reinforcing elements in a binder matrix material. Materials such as Portland cement, gypsum, epoxy and polyester thermoset resins, thermoplastics, etc. are often reinforced with fine filaments of glass, carbon, ceramic, wood pulp/cellulose and polymers or other fibers, particles or rods to provide improved strength, stiffness and toughness. Concrete (Portland cement with stone/rock aggregates and sand) uses steel or other rods or fibrous strands to provide engineering structures with high load carrying capabilities. These composite systems are produced in two basic design configurations:                1. Long or essentially continuous, aligned reinforcing elements disposed in the axes, planes or surfaces of applied force        2. Short, randomly-oriented reinforcing fibers uniformly dispersed throughout object        
High levels of properly placed reinforcement are required to improve matrix strength. However, the processes used to produce these composites are often quite complex and the resultant products are relatively costly. For instance, composites using long, aligned reinforcements, such as filament wound fiberglass reinforced plastics or pre-stressed steel/concrete, can achieve high reinforcement volume loading content (over 50% of composite volume) and correspondingly high strength, but the design flexibility is limited and manufacturing costs are high since these reinforcements must be individually and precisely placed into position. In the second case (composites using short, randomly dispersed reinforcements), fiber clumping, incomplete fiber/binder wet-out and poor flow or molding characteristics of the mixtures limit reinforcements to 10 to 20% maximum fiber volume for many types of common composite systems (i.e., polyester resin compounds with chopped graphite or glass fibers; fiberglass or cellulose fiber reinforced cement pastes; etc.). Sophisticated mixing and intensive pressing/molding/laminating/extrusion techniques are needed to achieve higher levels of reinforcement necessary to improve composite strength or other properties.
Often, unique and expensive processes such as filament winding; high pressure compression molding and extrusion; resin transfer, reaction and injection molding; paper-making processes; spray-up; centrifugal casting; etc. are required for various common types of composite materials. A reinforcing material that can be easily mixed or placed into the binder material and formed by simple means into both thin flat sheets and complex shapes would be highly desirable. Additionally, the reinforcements must provide the improved strength and other physical property benefits at an economical cost.
Extensive efforts have been made to accomplish these goals. To date no inventions have been identified that allow for a highly reinforced matrix material to be formed directly into a final product with acceptable costs and adequate mechanical property improvements. Reinforced polymer materials continue to be made largely by filament winding, extrusion, injection or compression molding, spray-up and other costly methods. Concrete still use pre-stressing or post-tensioning of steel wire or bars as the primary construction method. Some new products have been introduce that use recent advances in glass fiber, wood pulp and other technologies allowing the replacement of a variety of asbestos-cement materials that have been banned due to health-related problems from asbestos. Also, a few novel, commercial products that allow simple, cheap manufacture have been developed such as premixed polymer, carbon and stainless steel fiber reinforced cement blends and short fiber filled, extruded thermoplastic pellets. However, none of these products listed above provide simple manufacturing combined with adequate increased strength to allow for use in load-bearing or structural applications. The technologies suffer in one or more of the following areas,                1. Low reinforcement levels (generally, less than 10 to 20% by volume)        2. The need for expensive, complex processing equipment and manufacturing techniques (especially to achieve >50% volume reinforcement levels)        3. Minimal benefit to design strength limits (yield or deflection point) or other structural properties despite increased levels of reinforcement        4. Excessive material cost and/or poor reinforcing efficiencies (cost:benefit ratio)        
Often when improvements are made in one area, however, the other areas are either ignored or suffer other additional problems.
Prior art has followed various traditional paths to improve composite properties and manufacturing ability. Thermoset resins (cross-linked monomers) and thermoplastics (heat processed polymers) have focused on the adaptation of new production methods and equipment. The reinforcements still include traditional fine filaments or bundled strands of glass, carbon, Kevlar and similar fibers. Improvements in the formulations, sizings/coatings and fiber properties have been espoused, but the actual form and geometry of the reinforcements has remained largely unchanged (multiple filament strands). Issues remain on the best way to wet-out or coat the fiber surfaces and properly disperse or place them within the matrix. Whisker fibers (carbides, oxides, metals, etc.), reinforcing fillers (clay platelets, wollastonite, etc.) and similar concepts such as nanomaterial technology have been proposed and have met with limited success in improving reinforced plastics, but the high surface area of these materials requires special techniques to incorporate in the binders at even marginally high volume levels.
The field of reinforced cement has seen significant growth. The substitution of asbestos fiber with glass, cellulose, metal and polymer filaments in reinforcing cement has been especially pervasive. The technology has followed four distinct trends. First, many U.S. Pat. Nos. (5,989,335; 5,916,361; 5,705,233, etc.) declare the use of low volume levels of well dispersed fine filaments to be effective. None of these, however, can provide true reinforcing value. While the fibers may improve toughness, impact strength and the like, insufficient fiber levels are present to effect any improvement in initial cracking strength . . . making such composites unsuitable for any structural type applications. Second, many of the reinforcements are used in the form of fine filaments but are incorporated at high volume levels with specialized equipment or processing techniques. High pressure, intensive molding, extrusion, laminating, vacuum filtration, etc. have been used to overcome the natural tendency of long, fine fibers to resist consolidation. These fibers also tend to tangle and clump together, making product manufacture difficult. Various disclosures (U.S. Pat. Nos. 6,528,151; 5,733,671; 5,676,105; 5,108,679; et al) detail some of these various processing techniques using fine diameter filaments.
Thirdly, efforts to fabricate, bond or intertwine the filaments into thicker strands have been disclosed in several patents as a means of providing a more desirable fiber geometry (thicker resultant, effective fiber diameters). As specified, herein, these larger diameters are critical to improved wet-out/coating and dispersion/placement in the matrix material. However, these prior art claims do not accomplish the intended purpose as effectively as the use of discrete fibers of a solid/monolithic type structure. Specifically, the various described bonded fiber agglomerations do not provide identical properties to those fibers of the present invention. The bonded strands can become degraded or separated during mixing and molding operations. Furthermore, the individual filaments within the fiber strands can slip (shear bond failures) or break pre-maturely under stress from load forces on the composite. Also, the steps necessary to create the fiber bundles add cost and variability to their reinforcing properties. U.S. Pat. Nos. 6,423,134; 5,685,902; 4,923,517; etc. all propose the use of adhered fiber bundles or filament agglomerations which suffer from the drawbacks noted immediately above as well as other design flaws (excessive fiber length, low fiber volume loading, poor strength/stiffness, etc. as required per this novel invention).
Finally, a limited number of patents have proposed the use of reinforcements with fiber diameters within the range consistent with the present invention. However, in every case either the level of reinforcement or physical properties of the fibers were inadequate to realize any improvement in initial crack or deformation strength of the composite. U.S. Pat. Nos. 6,503,625; 5,443,918; 4,284,667 and similar ones detail the use of these larger fiber diameters. Most of these reinforcements are proposed to be used at levels of less than 10% volume loading. Typically, the referenced lengths of the reinforcements are too long to achieve higher levels, anyway, with a random three-dimensional dispersion of fibers. For instance, a 0.5 mm diameter, 20 mm long reinforcement (40:1 L:D aspect ratio) is not capable of achieving volume levels much greater than 10-20% unless high pressure or mechanical working is used to bend or crush these miniature rods into a more dense packing arrangement. The present invention also differs from reinforced concrete that uses long or continuous steel wire or rebar for strength enhancement. While this type of concrete employs large diameter reinforcement similar to the requirements of the present invention (1.5 to 15 mm diameter), common practice uses less than 10% steel by volume in typical construction. The novel proposed technology requires the use at least 20-40% volume and for aligned, uniaxial reinforcements the total volume levels should preferably reach as much as 70% or more. While a steel reinforced concrete composite incorporating this much reinforcement might not be desirable, other materials (eg., long, 5-15 mm diameter fired clay, ceramic or glass rods), alone or in combination with steel members could provide a composite with a superior combination of strength and cost trade-offs. Calculations show that a cement composite with high levels of large diameter, fired clay rod reinforcement might allow for a 50% reduction in both product weight and costs with comparable strength properties relative to traditional steel reinforced concrete.